The present invention relates to a system that combines a passive speed detection system with an active speed detection system and then transmits the information obtained to one or more end users.
U.S. Pat. No. 5,586,063, which is assigned to the assignee of the present invention and is incorporated herein, sets forth a practical passive electro-optical speed and distance measuring system. Summarily, this passive system includes a pair of camera lenses positioned along a common baseline a predetermined distance apart and to capture images of a target at different times. The camera lenses are focused on light sensitive pixel arrays which capture target images at offset positions in the line scans of the pixel arrays. A video signal processor with a computer determines the location of the offset positions and calculates the range to the target by solving the trigonometry of the triangle formed by the two camera lenses and the target. Once the range to the target is known at two different times the speed of the target is calculated.
There are also many active speed detection systems, the most common of which are laser and radar speed detection systems. Active speed detection systems require a transmitter to transmit energy towards a moving target which is then reflected back to a receiver. Various schemes are then used for measuring the time of transmission and the signal return or Doppler frequency shift-in order to calculate the range to the target and its speed.
Active speed detection systems have several problems. For example, generally a trained operator must aim the transmitter at the object of interest and trigger the system at the proper time. Further, if the transmitter is left on continuously, the transmitter can easily be detected and circumvented. Since these systems are not imaging systems they cannot identify the objects. Accordingly, identification may be accomplished by a human operator at the measurement site that can add human error, by a still film camera that is unable to provide images in real time and therefore cannot be acted upon immediately, or by film or video recording which is slow, bulky, expensive, and limits the number of images that can be captured. Further, images of the targeted object acquired by these systems cannot be quickly transmitted to a remote location.
It should be noted that there are specific problems related to active laser speed detection systems. For example, because of the narrow beam-width of the laser, it must be carefully aimed at an object of interest by a trained operator.
It also should be noted that there are specific problems related to active radar speed detection systems. For example, if the radar is unattended and continuously transmitting, it is easily detected and circumvented. Further, the transmitted and received radar beam angle is so wide that the radar beam can often be reflected from other moving objects in addition to the targeted object. Radar beam reflections from multiple moving objects are a common source of error with Doppler radar systems and limit the conditions under which they can be used.
Combining different-technology sensor systems into a single system where each sensor covers part or all of the same field-of-view is called xe2x80x9csensor fusion.xe2x80x9d This approach is used in a number of military weapons systems to circumvent the limitations of any one sensor technology. For example, millimeter-wave radar systems have been combined with imaging infrared sensors in battlefield imaging sensors used for munitions aiming and guidance.
Problems also exist with known combination systems such as photo/laser and photo/radar systems. For example, photo/laser systems do not provide a speed measurement independent of the laser gun. Photo/radar systems do not provide speed measurement independent of the radar and also do not provide distance information. Photo/radar systems emit signals that are easy to detect and circumvent. Neither photo/laser systems nor photo/radar systems provide an image in real time to support immediate pursuit of speeders.
What is needed is a speed measurement system that overcomes the aforementioned problems of known systems.
The combination of a passive speed detection system and an active speed detection system can measure highway vehicle speeds and distances. Preferably the passive speed detection system is the passive electrooptical (EO) speed and distance measuring system disclosed in U.S. Pat. No. 5,586,063, which is assigned to the assignee of the present invention and is incorporated herein. Preferably the active speed detection system is either a conventional laser system or a conventional radar system. The active and passive systems can be used separately and in various combinations depending on conditions and specific features desired.
The combination system improves the efficacy of the conventional active systems and provides additional features not possible with the traditional active systems alone. For example, radar alone cannot provide a distance measurement and laser alone cannot provide real-time recording and production of video images.
Some of the possible advantages of a combination passive/active speed detection system include: the ability to provide an image of the object pointed at by the active system; the video image of the measured object is provided in real-time; the video image and data may be transmitted immediately to one or more remote locations; the electronically-recorded images may be automatically sorted by computer software based on parameters such as calendar date, time-of-day, speeds, and frequencies-of-occurrence; two independent measurements of object speed can be automatically compared to increase the confidence level in both measurements; in certain operating modes the active system may be automatically actuated by the passive system at the correct object distance thus allowing for unmanned operation; the ability to provide an object image, speed and distance history up to, at the time of, and following the measurements; and the decrease in the susceptibility of the active system to defeat by countermeasures.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.